Abstract.

Thanks to technologies such as light detection and ranging (LiDAR), power line inspection has recently become automated. LiDAR is used to assess the condition of wires and supports, create terrain maps for upgrading existing lines or laying new ones, and assess the risks of vegetation’s influence on the integrity of structures, which is vital for industrial activities and human life.

The sections covered will be Introduction to LiDAR, Powerline Inspection, How Lidar can help with Powerline Inspection, and Using RESEPI for Powerlines Inspection. Finally, the benefits of using LiDAR in Powerline Inspection will be summarized.

Section 1. Introduction to LiDAR

Lidar (Light Detection and Ranging) works by emitting laser pulses and measuring the time it takes for them to return after reflecting off objects. When lidar emits a laser pulse, it travels at the speed of light. When a pulse hits an object, it is reflected to the lidar, Figure 1. A lidar system measures the time that elapses from when a pulse is emitted until it returns.

 

Figure 1. Conditional demonstration of LiDAR operation.

Knowing the speed of light and the time it takes for the pulse to return, the lidar can accurately calculate the distance to the object. For most modern lidars, this process is repeated at least 240k times per second, allowing the lidar to create detailed 3D maps of the environment. The distance data is combined to produce a point cloud showing objects’ shape and location within the lidar field of view.

Variations among LiDAR models primarily include differences in scanning angle, maximum scanning range, and scanning precision. Most contemporary LiDAR devices offer multiple scanning modes. For instance, the RESEPI XT32 can adjust rotation speed, scanning angle, and the number of returns, thereby impacting the density of the point cloud and the laser’s ability to penetrate through obstacles like trees and grass [1].

Integrating LiDAR with an inertial navigation system (INS) results in a system capable of georeferencing each point with centimeter-level precision and accuracy [2]. An example of such an integrated device is the Inertial Labs RESEPI Payload [3]. This compact device is fully customizable to accommodate various applications, offering options such as camera inclusion, LiDAR model selection, and GNSS receiver. It’s commonly utilized for drones and other small, unmanned aircraft systems (sUAS).

After data collection by LiDAR payloads like RESEPI, it is crucial to subject the raw data to post-processing before generating the point cloud. For this purpose, Inertial Labs has developed specialized software – PCMasterPro [4]. This software streamlines the post-processing procedure, requiring minimal manual intervention and ensuring seamless integration with hardware and software components.

Section 2. Powerline Inspection

Power line inspection methods include visual inspection, thermography, ultrasonic inspection, and vibration analysis. Below is a brief description of each.

1. Visual inspection – direct inspection of power lines by specialists on the ground or using a lift to reach a height. A visual inspection can reveal defects such as damaged insulation, corrosion of wires or supports, insulator cracks, and other visible damage [5].
   1. Advantages:
      • Simplicity
      • Accessibility
      • Possibility of immediate action
   2. Disadvantages:
      • Requires significant labor and time
      • limited by the ability to access hard-to-reach sections of lines
      • Quality of work is affected by the experience and competence of specialists

2. Thermography – uses infrared cameras to detect temperature anomalies that can indicate potential problems such as overheating of wires, connections, and equipment [5].
   1. Advantages:
      • Allows you to identify problems at an early stage
      • Can be carried out from the ground or a helicopter/drone in manual or automatic mode, making it easier to access hard-to-reach areas
   2. Disadvantages:

• Requires special equipment and personnel training
• Not all defects can be detected

3. Ultrasonic inspection – uses ultrasonic devices to identify defects that may not be visible by visual inspection. This method is especially effective for diagnosing the condition of insulators and connections [6].

1. 1. Advantages:

• High accuracy in detecting hidden defects
• Can be used to check the condition of internal components

2. Disadvantages:

• Requires special equipment and personnel training
• Limited area of application
  • For example, it is unsuitable for testing long-line sections.

        4. Vibration analysis – involves using sensors to measure vibrations of wires and equipment. Abnormal vibrations may indicate mechanical problems or malfunctions [7].

1. Advantages:

• Allows you to monitor the status of lines in real time
• Effective for identifying mechanical defects.

2. Disadvantages:

• Requires installation of sensors on the lines, while the area analyzed by one sensor is limited
• Significant financial investments are required to monitor long power lines
• Data analysis can be complex and require specialized software

Ultrasonic inspection and vibration analysis are combined to provide more complete and accurate condition monitoring of power lines.

Inspection automation includes using all the above methods, except that visual inspection is carried out by photo or video cameras, hyperspectral, and infrared cameras, and the data is processed using artificial intelligence. Below are some examples to explain some use cases with automation.

1. Use of robots – various designs are used for this purpose. These are mainly climbing or sliding robots that can navigate supports or ride along wires. Ground robots help patrol substations and can be equipped with various sensors such as gas detection, ultraviolet sensors for corona detection, directional microphones, and high-definition optical cameras [8 – 10].

1. Advantages:

• Can be suspended from power lines or explore infrastructure on the ground
• Allows you to carry more equipment

2. Disadvantages:

• Slow movement speed [11]
  • For example, for a robot that is suspended on wires, the speed of movement = 1.6 km/h, and the operating time on one charge is 8 h; therefore, the path covered by the robot in 8 hours = 12.8 km. For RESEPI Payload, the recommended drone flight speed = is 18 km/h; in just 20 minutes, the user can explore 6 km of power lines.
• Specialists are required to hang the robot on the wires

2.   Stationary inspection: Many sensors and cameras, including those listed earlier, are installed on power lines, Figure 2 shows.

1. Advantages:

• Can provide data on the condition of objects 24/7

2. Disadvantages:

• Requires significant investment to automate the data collection process, especially for long sections of power lines
• It’s not always possible to install sensors in hard-to-reach places

 

Figure 2. Stationary inspection sensors.

              3.  Air inspection – helicopters or drones equipped with lidars and various surveillance cameras can be used [12].

1. Advantages:

• High flight speed allows you to explore many kilometers of lines and supports in the shortest possible time

2. Disadvantages:

• The ability to fly is affected by weather conditions

Inspection of power lines has recently transformed from classical methods to almost complete automation of the process.

Section 3. How can Lidar help with Powerline Inspection?

LiDAR technology has emerged as a powerful tool for monitoring powerlines, offering numerous advantages over traditional methods. Therefore, Inertial Labs has created a product that will solve many problems associated with monitoring powers [13]. Some of these solutions include:

• It is not unusual for powerline support to be in a difficult-to-access area, as shown in Figure 3. If manual methods were used, special machinery would have to be used, which would take time and money. The same is true for robotic means. With a LiDAR drone, it is possible to fly overpower lines and obtain a point cloud from which a map of elevations and terrain can be obtained to properly plan the construction of new supports or the modernization of existing supports, as well as the energy-consuming utility systems at the connected facilities.

 

Figure 3. Powerline supports are in a difficult-to-access area.

• As is known, vegetation near power lines can lead to accidents since strong winds can cause trees to break and cut off the wires. To prevent this from happening, regular monitoring is carried out of the distance from the crowns of trees and other vegetation to the cables, and decisions are made on the need for timely removal of vegetation that poses the greatest threat to the stability of the powerline, Figure 4.

 

Figure 4. Vegetation near powerlines.

In places where the terrain is uneven, manually determining the distance from the crowns of trees and other vegetation is inconvenient and expensive because this may require workers’ insurance or special equipment. However, LiDAR will be fast and profitable because all the necessary information will be available in one flight over the powerline.

• Ground surveys are time-consuming, labor-intensive, and very expensive. Aerial photography allows us to cover a large area and determine wire profiles for timely removal of sagging. This is especially useful if the supports are arranged in several rows, Figure 5.

 

• Inertial Labs has implemented SLAM technology in its PCMasterPro point cloud generation software [14]. This technology allows the RESEPI payload to be mounted on a tracked or wheeled robot, making ground-based scanning of power substations possible.

After obtaining a highly accurate point cloud from PCMasterPro, thanks to third-party software (LiDAR360, TerraScan, etc.), users can georeferenced SLAM data, obtaining integrated data obtained from ground and airborne scanning [15, 16]. In addition, these programs have tools for automatically classifying power line elements and detecting danger points.

LiDAR payloads like Inertial Labs’ RESEPI have an integrated camera to produce highly accurate geo-referenced and colored point clouds. Another advantage of using the camera, besides colorization of the point cloud, is the more significant number of images that can be used for visual inspection or photogrammetry. Because the lidar does not need additional lighting, data recording can be done at any time of day if no camera is required.

LiDAR inspections of transmission lines allow grid operators to save time and money and prevent lost profits due to power outages by taking suitable measures based on reliable and accurate information.

Section 4. Using RESEPI for Powerlines Inspection.

Now, let’s look at the capabilities of RESEPI Payload for powerline scanning in a real-case scenario. The primary objective was to determine wire sag in dense vegetation and hilly terrain.

For this purpose, a flight mission was organized to scan a problematic power line section.

Mission objectives:

• Get a point cloud of power lines and their supports
• Determine wire sag
• Determine the distance from vegetation to wires

The RESEPI Payload was strategically designed for multiple application bases with mounting options for mobile vehicles, DJI-supported drones (DJI M300, M600 Pro), custom drones, handheld platforms, vehicles, the Freefly Alta-X, and many more. Therefore, choosing a drone was no problem. For the mission, DJI M300 and RESEPI XT-32M2X were used. Specifications of the XT-32M2X laser are shown in Figure 6.

 

Figure 6. RESEPI XT-32M2X technical characteristics.

The lidar was chosen because it has a triple return, providing quality cabling and forestry encroachment detailing surrounding the power lines. As can be seen in Figure 7, all wires are captured in the point cloud, which might not have happened if the lidar had only one return. In addition, the point cloud accurately georeferences UTM coordinates.

The data collection time took about 15 minutes. The drone flew over the line 2 times in forward and reverse direction at a speed of 7 m/s and an altitude of 70 meters.

 

Figure 7. The powerline point cloud is colored by intensity and opened in Cloud Compare.

The user then performed post-processing in PCMasterPro, which took 30 minutes, and opened the point cloud in “Cloud Compare” for measurements [17]. Figure 8 shows the linear distance between the wire fastenings, which is 535.48 m. Based on this information and the wires’ parameters, the user could easily calculate the sag. Members of Electrical4U describe how this is calculated in detail [18].

 

Figure 8. Powerline distance of one section.

The final goal of the mission was to measure the distance from the nearest vegetation to the wires. In just a couple of minutes, the place where the tree crown was closest to the wires was discovered, and in a couple of clicks, the distance was measured, as shown in Figure 9. Knowing this distance, the user removed several trees, according to the required standard [19].

 

Figure 9. Measuring the distance from tree crowns to wires.

With RESEPI Payload, the user could quickly get a point cloud in just a few hours and inspect the section of power lines they were interested in without using special equipment and spending extra money. This project required only a drone, a lidar, and a base station.

Conclusion.

Powerlines are critical infrastructures that must be periodically inspected to ensure a reliable power supply and compliance with regulatory requirements. Regular preventive maintenance ensures your electrical system operates at total capacity.

Therefore, it is vital to organize your inspection as efficiently as possible, and this is where LiDAR data collection and processing can help. Unlike traditional manual methods, LiDAR data collection is much faster, and the user receives a 3D point cloud and camera photos. Thanks to this, it is possible to solve a wide range of problems: determining the sagging of wires, assessing the risks of the influence of vegetation, and constructing digital maps (digital surface models and digital elevation models) for planning the modification of existing lines and the construction of new ones.

The transmission line example demonstrates that payloads such as RESEPI Payload can make monitoring fast and efficient. With RESEPI Payload, it is easy to determine the sagging of wires and the distance to tree crowns without resorting to manual methods and expensive machinery.

Inertial Labs is committed to providing high-quality, customizable solutions that are of excellent value for money at an affordable price.

References.

[1] “XT32 | Mid-Range Mechanical Lidar | HESAI Technology.” HESAI, www.hesaitech.com/product/xt32/. Accessed 3 June 2024.

[2] Wikipedia Contributors. “Inertial Navigation System.” Wikipedia, Wikimedia Foundation, 21 May 2019, en.wikipedia.org/wiki/Inertial_navigation_system.

[3] “RESEPI – LiDAR Payload & SLAM Solutions.” RESEPI, lidarpayload.com. Accessed 3 June 2024.

[4] Inertial Labs. “RESEPI Quick-Start Guide – Setting up Your LiDAR Survey System and PCMaster – Inertial Labs.” YouTube, 4 Aug. 2022, youtu.be/AygQTBVNrKw. Accessed 3 June 2024.

[5] Chen, Minghao, et al. “Environment Perception Technologies for Power Transmission Line Inspection Robots.” Journal of Sensors, vol. 2021, 30 Mar. 2021, pp. 1–16, https://doi.org/10.1155/2021/5559231.

[6] Branham, Stephanie, et al. Nondestructive Testing of Overhead Transmission Lines.

[7] Aoki, Emi, et al. “Vibration-Based Status Identification of Power Transmission Poles.” IFAC-PapersOnLine, vol. 55, no. 27, 1 Jan. 2022, pp. 214–217, https://doi.org/10.1016/j.ifacol.2022.10.514. Accessed 5 June 2024.

[8] Michele Guarnieri. “Expliner – Robot for Very High Power Lines Inspection.” YouTube, 31 Jan. 2011, www.youtube.com/watch?v=vCJ0WL8XX-k&ab_channel=MicheleGuarnieri. Accessed 5 June 2024.

[9] Hydro – Quebec. “LineRanger: Une Revolution En Robotique de Lignes de Transport.” YouTube, 6 Mar. 2018, www.youtube.com/watch?v=oTlj1aioUV8&ab_channel=Hydro-Qu%C3%A9bec. Accessed 5 June 2024.

[10] Porter, Kathryn. “Drones and Droids: Automated Power System Monitoring.” Watt-Logic, 25 Feb. 2021, watt-logic.com/2021/02/25/drones-and-droids/. Accessed 5 June 2024.

[11] “Expliner.” ROBOTS: Your Guide to the World of Robotics, robotsguide.com/robots/expliner.

[12] Guan, Hongcan, et al. “UAV-Lidar Aids Automatic Intelligent Powerline Inspection.” International Journal of Electrical Power & Energy Systems, vol. 130, Sept. 2021, p. 106987, https://doi.org/10.1016/j.ijepes.2021.106987.

[13] “RESEPI – LiDAR Payload & SLAM Solutions.” RESEPI, lidarpayload.com. Accessed 5 June 2024.

[14] Wikipedia Contributors. “Simultaneous Localization and Mapping.” Wikipedia, Wikimedia Foundation, 8 July 2019, en.wikipedia.org/wiki/Simultaneous_localization_and_mapping.

[15] “LiDAR360 Software and Real-Time Point Cloud Display.” Www.greenvalleyintl.com, www.greenvalleyintl.com/LiDAR360/.

[16] “Terrasolid – Software for Point Cloud and Image Processing.” Terrasolid, 21 Sept. 2023, terrasolid.com/.

[17] “CloudCompare – Open Source Project.” Www.danielgm.net, www.danielgm.net/cc/.

[18] https://www.facebook.com/electrical4u. “Sag in Overhead Conductor | Electrical4U.” Electrical4U, 24 Feb. 2012, www.electrical4u.com/sag-in-overhead-conductor/.

[19] FAC-003-3 Minimum Vegetation Clearance Distances. 2015.